1) Field of the Invention
The present invention relates to a method for packaging and assembly of electronic units and more particularly to packaging and assembly of electronic units requiring mechanical robustness and being used in rugged environmental conditions such as e.g. demanded by electronic devices used in industrial machinery and automotive control units.
2) Prior Art
Electronic units as addressed by the present invention are preferably small scalable electronic devices or embedded electronic devices, e.g. handheld devices, set-top systems, internet appliances, mainly used in rugged environmental conditions such as e.g. demanded by electronic devices used in industrial machinery tools and automotive electronic units. They normally comprising at least a processor, a storage media (ROM, RAM), and interfaces, e.g. interfaces to user and/or components to be controlled. The electronic unit itself is mostly arranged in a housing. The electronic components being part of the electronic units may be arranged in the housing either in a card-on-board system or a card stack system.
Typically card-on-board systems utilize a base planar-board (mother board) featuring extension slots and connectors allowing to customize/scale the system by adding on various system feature cards. The minimum base system is providing the overhead on power-source signal drive capability and electrical connectors supporting to assemble system configuration. As a result, it is necessary that the electronic components positioning within the housing of the electronic units be maintained. In addition, many card-on-board systems are developed to satisfy the requirements of a particular electronic assembly. Therefore, as the system size and configuration changes, an additional package is required which would also require changes on the mother-board. As a result, packaging for electronic units is relatively expensive.
Card stack systems provide a multi-planar-board system. The basic system functions as well as the potential system expansions are sub-divided and implemented into individual single planar boards. The single boards are rigidly stacked in a housing and separated by spacers. Electrical contacts and the signal drive between the single planar boards are achieved via specifically designed connectors. Finally, the multi-planar board system is separated from the housing of the electronic unit by a shock absorbing arrangement. The prior art card stack system does provide scalable electronic units. But by requiring precisely arranging the single boards in a rigid stacked arrangement in the housing, by providing the exact interconnections between the boards, and by providing shock-absorbing components the prior art stack system requires an expensive and time-consuming manufacturing and assembly process. As a consequence, overall cost of such prior art systems tends to be high.
U.S. Pat. Nos. 3,904,934 and 3,529,213 disclose examples of those prior art card stack systems.
In view of the above there is a need for a card stack system that corrects the problems of the prior art card stack systems.